Method of grinding a cutter for skive-machining and device for grinding the skive-machining cutter

ABSTRACT

A method of grinding a cutter for skive-machining a work and a device for grinding the skive-machining cutter which method and device allow formation of a better gear with a cutting operation. The target of grinding is a skive-machining cutter in which a plurality of helical groove portions are formed. A first grinding step is effected for grinding one of a pair of blade lateral faces facing the groove portion. A second grinding step is effected for grinding the other of the pair of blade lateral faces. Then, a third grinding step is effected for forming a blade tip face to be continuous with the blade lateral face formed in the first grinding step and the blade lateral face formed in the second grinding step.

TECHNICAL FIELD

The present invention relates to a method of grinding a cutter forskive-machining a work and relates also to a device for grinding theskive-machining cutter. More particularly, the invention relates to atechnique of finishing a cutting blade portion of a skive-machiningcutter.

BACKGROUND ART

Patent Document 1 discloses a mode of machining in which a ring-shapedwork is rotated and a skive-machining cutter (a pinion cutter in thisdocument) rotated in synchronism with this work is fed along atooth-trace (tooth helix) direction of teeth to be formed in the work,thus effecting a tooth-cutting operation.

According to this Patent Document 1, the skive-machining cutter isconfigured like a helical gear, and this skive-machining cutter and thework are rotated in synchronism. In association with this, a cuttingoperation proceeds with the cutting blade portion of the cutter engaginginto the respective tooth grooves of the teeth to be formed in the work,thus realizing the machining.

As this skive-machining cutter is configured like a helical gear, thecutter can be manufactured by a similar operation used for a helicalgear.

Patent Document 2 discloses a method of gear-forming cutting capable offorming a helical gear also, in which there are provided a grindstonefor grinding one face of a tooth groove of a teeth-formed work and agrindstone for grinding the other face of the tooth groove, and grindingoperations are carried out with these grindstones.

PRIOR-ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2012-45687

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 7-112320

SUMMARY OF THE INVENTION Problem to be Solved by Invention

The cutting blade portion of a skive-machining cutter has a same shapeas that of a helical gear, but differs therefrom in its function. Forthis reason, the respective portions of the skive-machining cuttercorresponding respectively to a tooth tip, a tooth face, a tooth bottom,a tooth thickness, a tooth shape, and a tooth trace will be designatedas a blade tip, a blade lateral face, a blade bottom, a blade thickness,a blade shape and a blade trace, respectively. Similarly, a toothcutting at the time of a machining of a gear will be explained as ablade cutting in the case of the skive-machining cutter.

When a skive-machining cutter is manufactured, for instance, like thecase of a gear, a turning operation is effected for shaping materialinto a cylindrical shape. Then, with a blade cutting operation of thecylindrical material (corresponding to a tooth cutting operation of agear), a cutting blade portion in the form of a gear tooth is formed andthen this is subjected to a heat treatment. Thereafter, a grindingoperation using a grindstone is effected for grinding blade lateralfaces, a blade bottom face, a blade tip face (corresponding to the toothfaces, the tooth bottom and the tooth tip, in the case of the gear).

With the skive-machining cutter, a protruding side thereof protrudingalong the rotational axis functions as the cutting blade portion, so theshape of the cutting blade portion formed like a gear tooth is reflectedin the shape of a tooth to be formed in the work.

For the reason described above, it is required that the blade shape andthe blade thickness of the cutting blade portion of the skive-machiningcutter be finished with high precision. Further, in forming the bladelateral faces, the blade bottom face and the blade tip face, a grindingoperation using a grindstone is effected generally. More specifically,as shown in Patent Document 2, by grinding one lateral face of the toothfaces and the other lateral face of the same with different grindstones,the tooth surface can be finished with higher precision.

In case two gears mesh each other, the respective tooth faces thereofcome into contact with each other for force transmission. Therefore, theshapes of the tooth tip and the tooth bottom in which no contact occursdoes not affect the force transmission. On the other hand, in the caseof the skive-machining cutter, the shape of the cutting blade portion isreflected directly in the shape of the tooth in the work, so highprecision is required in the shape of the region extending from theblade tip face to the blade lateral face.

In particular, in case the blade lateral face and the blade tip face ofthe cutting blade portion are formed in a simple manner, this may resultin formation of a stepped portion at the boundary between the bladelateral face and the blade tip face, due to difference of theirmachining steps, and this stepped portion will appear in the shape ofthe gear of the work. Hence, this remains room for improvement in thisrespect. Moreover, in case such stepped portion is formed at theboundary between the blade lateral face and the blade tip face, there ispossibility of the cutting blade portion being damaged by stressconcentration at the time of cutting operation. Thus, there remains roomfor improvement in this regard also.

The object of the present invention is to configure rationally a methodof grinding a cutter for skive-machining a work and a device forgrinding the skive-machining cutter which method and device allowformation of a better gear with a cutting operation.

According to a characterizing feature of an inventive method, a methodof grinding a skive-machining cutter having a plurality of cutting bladeportions formed by forming a plurality of groove portions helicallyabout a rotational axis in an outer circumference of a material so thatthe plurality of cutting blade portions are arranged at positionsbetween respective adjacent pairs of the groove portions and radiallyabout the rotational axis, the method comprises:

a first grinding step for grinding one of a pair of blade lateral facesfacing the groove portion;

a second grinding step for grinding the other of the pair of bladelateral faces; and

a third grinding step for grinding a blade tip face in a regionextending from the pair of blade lateral faces to a projecting side ofthe cutting blade portion;

wherein an order is set such that the third grinding step is effectedafter the first grinding step and the second grinding step; and

wherein in the third grinding step, a grinding operation is effectedsuch that the blade tip face formed by grinding is formed steplesslycontinuous with the one blade lateral face formed by the first grindingstep and the other blade lateral face formed by the second grindingstep.

With the above-described method, one blade lateral face is ground by thefirst grinding step and the other blade lateral face is ground by thesecond grinding step. Thus, compared with a method in which the pair ofblade lateral faces are ground by a single step, the pair of bladelateral faces can be formed individually with high precision.Thereafter, as the blade tip face is ground by the third grinding step,the blade tip face can be formed steplessly continuous with the leadingside blade lateral face and the trailing side blade lateral face.Further, according to this method, the grinding operations of thegrinding in the first grinding step and the grinding in the secondgrinding step can be effected individually. Thus, if a blade thickness(corresponding to the tooth thickness of a gear) is to be adjusted, thisadjustment can be effected by the same technique as a lateraldislocation of a gear.

In particular, when a work is machined by a skive-machining cutterground by the above method, it is possible to form tooth faces which aresmoothly continuous with each other. Further, in the case of thearrangement in which a stepped portion is formed at the boundary betweenblade lateral faces and a blade tip face of a cutter, at the time ofcutting, stress concentration will occur at the portion of this steppedportion, which can lead to such a damage as a “chipping” or the like. Onthe other hand, in the case of the cutter ground by the method of thepresent invention, no stepped portion is formed at the boundary betweenthe blade lateral faces and the blade tip face, so that no stressconcentration will occur at this portion; thus, the service life of thecutter can be extended.

Therefore, it has been made possible to configure a method of grinding askive-machining cutter capable of forming a gear in a favorable mannerby cutting and providing also an extended cutter service life.

In the present invention, the first grinding step may employ a disc-likegrindstone having a grinding face having a shape along the one bladelateral face and driven to rotate for the grinding operation and thesecond grinding step may employ a disc-like grindstone having a grindingface having a shape along the other blade lateral face and driven torotate for the grinding operation.

With the above, by the grinding operation associated with drivingrotation of the first grindstone, a blade lateral face corresponding toits grinding face is formed and by the grinding operation associatedwith driving rotation of the second grindstone, a blade lateral facecorresponding to its grinding face is formed. With this, it becomes alsopossible to form the pair of blade lateral faces in different shapeswith even higher precision.

In the present invention, the third grinding step may employ agrindstone having a grinding face along the blade tip face and driven torotate for the grinding operation; and the blade tip face formed by thisthird grindstone is formed continuous with the one blade lateral faceformed by the first grindstone and the other blade lateral face formedby the second grindstone.

With the above, with the driving rotation of the third grindstone, ablade tip face corresponding to its grinding face is formed smoothlycontinuous with the pair of blade lateral faces. Thus, the blade tipface smoothly continuous with the pair of blade lateral faces can beformed with high precision.

In the present invention, the grinding operation of the blade lateralface may be effected by moving at least one of the first grindstone andthe second grindstone toward a circumferential direction about therotational axis by an amount needed for adjustment of blade thickness.

With the above, in grinding a blade lateral face of the skive-machiningcutter, as at least one of the first grindstone and the secondgrindstone is moved relative to the skiving cutter in thecircumferential direction about the rotational axis and an amount ofthis relative movement is set to an amount needed for blade thicknessadjustment, there is realized adjustment of blade thickness(corresponding to tooth thickness of a gear).

This machining technique is same as the technique of a lateraldislocation of a gear which is effected when a tooth thickness of a gearis adjusted, so there is involved no change in the blade shape(corresponding to the tooth shape of the gear). In contrast, in case agrinding amount were increased by moving one of the first grindstone andthe second grindstone closer to the rotational axis in the same manneras the lateral dislocation of a gear, this would lead to inconvenienceof inadvertent change in the blade shape. On the other hand, in the caseof the present invention, a required blade thickness is obtained withoutchanging the blade shape, with utilization of the technique of lateraldislocation.

In the present invention, in the third grinding step, the grindingoperation may be effected by buff or blast of shot peening material.

With the above, unlike grinding by a grindstone, the vicinity of a faceto be ground is ground also. Thus, without effecting any specialmachining, the stepped portion at the boundary portion between the bladetip face formed by the grinding in the third grinding step and the bladelateral faces can be minimized for allowing the blade tip face and theblade lateral faces to be formed smoothly continuous with each other.

An inventive device comprises:

a cutter supporting section for a skive-machining cutter having aplurality of cutting blade portions formed by forming a plurality ofgroove portions helically about a rotational axis in an outercircumference of a material so that the plurality of cutting bladeportions are arranged at positions between respective adjacent pairs ofthe groove portions and radially about the rotational axis;

a first grinding section for grinding one of a pair of blade lateralfaces facing the groove portion;

a second grinding section for grinding the other of the pair of bladelateral faces;

a third grinding section for grinding a blade tip face in a regionextending from the pair of blade lateral faces to a projecting side ofthe cutting blade portion; and

a controlling section for controlling the device such that grindingoperations by the first grinding section and the second grinding sectionare effected on the skive-machining cutter supported to the cuttersupporting section and then a grinding operation is effected by thethird grinding section for forming the blade tip face steplesslycontinuous with the one blade lateral face formed by the first grindingstep and the other blade lateral face formed by the second grindingstep.

With the above-described configuration, while the skive-machining cutteris supported to the cutter supporting section, one blade lateral face isground by the first grinding section and the other blade lateral face isground by the second grinding section. Thus, compared with a method inwhich the pair of blade lateral faces are ground simultaneously, thepair of blade lateral faces can be formed individually with highprecision. Thereafter, as the blade tip face is ground by the thirdgrinding section, the blade tip face can be formed steplessly continuouswith the pair of blade lateral faces. Further, according to thisconfiguration, the grinding operations of the grinding by the firstgrinding section and the grinding in the second grinding section can beeffected individually. Thus, if a blade thickness (corresponding to thetooth thickness of a gear) is to be adjusted, this adjustment can beeffected by the same technique as a lateral dislocation of a gear.

In particular, when a work is machined by a skive-machining cutterground by the device having the above configuration, it is possible toform tooth faces which are smoothly continuous with each other. Further,in the case of the arrangement in which a stepped portion is formed atthe boundary between blade lateral face and a blade tip face of acutter, at the time of cutting, stress concentration will occur at theportion of this stepped portion, which can lead to such a damage as a“chipping” or the like. On the other hand, in the case of the cutterground by the device of the present invention, no stepped portion isformed at the boundary between the blade lateral face and the blade tipface, so that no stress concentration will occur at this portion; thus,the service life of the cutter can be extended.

Therefore, it has been made possible to configure a grinding device forgrinding a skive-machining cutter capable of forming a gear in afavorable manner by cutting and providing also an extended cutterservice life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a cutter and a work at the time ofa skive-machining,

FIG. 2 is a section view showing the cutter and the work at the time ofa skive-machining,

FIG. 3 is a schematic showing a configuration of a grinding device,

FIG. 4 is a view illustrating a manufacturing process of the cutter,

FIG. 5 is a perspective view showing cutting blade portions of thecutter in enlargement,

FIG. 6 is a section view showing the cutting blade portions of thecutter under roughly ground state thereof,

FIG. 7 is a section view showing a ground state by a first grindstone,

FIG. 8 is a section view showing a ground state by a second grindstone,

FIG. 9 is a section view showing a state immediately before grinding bya third grindstone,

FIG. 10 is a section view showing a ground state by the thirdgrindstone,

FIG. 11 is a section showing the cutter after grinding,

FIG. 12 is a section showing a grinding state by a “double-function”grindstone in a further embodiment (a), and

FIG. 13 is a section showing a ground state by a third grindstone in thefurther embodiment (a).

MODES OF EMBODYING THE INVENTION

Next, embodiments of the present invention will be explained withreference to the accompanying drawings.

[General Description of Skive-Machining]

A skive-machining cutter (to be referred to as a “cutter 10” in shorthereinafter) is for use in a skive-machining device shown in FIG. 1 andFIG. 2 for forming a flat internal gear by cutting an innercircumferential face of a ring-shaped work 1. This skive-machiningdevice realizes its machining by operations similar to those disclosedin Japanese Unexamined Patent Application Publication No. 2012-45687 andJapanese Unexamined Patent Application Publication No. 2012-51049.

With this skive-machining device, the work 1 is supported to a table 2which is rotated about a vertical axis Y and a cutter 10 is supported tobe rotatable about a rotational axis X having a positional relationshipoffset from the vertical axis Y. The cutter 10 has, in its outercircumference, a plurality of cutting blade portions 11 like a helicalgear. As the rotational axis X is tilted by a tilt angle α relative tothe vertical axis Y, a blade trace (blade helix) direction of thecutting blade portion 11 to come into contact with the inner face of thework 1 is aligned with a tooth trace (tooth helix) direction of a toothto be formed in the work 1.

More particularly, in order to allow the cutting blade portion 11 of thecutter 10 to come into contact with the inner circumferential face ofthe work 1 under a posture parallel with the vertical axis Y, thiscutting blade portion 11 is formed like a helical gear tooth and thetilt angle α is set so as to create such relative posture as above.

Under the above-described condition, the work 1 is rotated in a mainrotational direction R about the vertical axis Y and also the cutter 10is rotated in a driven rotational direction S about the rotational axisX such that a moving rate of the inner circumference of the work 1 maybe equal to a moving rate of the outer circumference of the cuttingblade portions 11 of the cutter 10, and also the cutter 11 is moved in ashifting direction Z along the vertical axis Y. With these, a cuttingoperation is realized.

[Features of Cutter]

As shown in FIG. 1, FIG. 2, FIG. 5, and FIG. 6, in the cutter 10, aplurality of groove portions 10A are formed helically about therotational axis X in an outer circumference of a material so that theplurality of cutting blade portions 11 are formed at positions betweenrespective adjacent pairs of the groove portions 10A. With this, theplurality of cutting blade portions 11 are formed radially about therotational axis X and the cutter 10 obtains a gear-like cross sectionalshape.

Further, of each cutting blade portion 11, portions thereof facing thepair of adjacent groove portions 10A will be designated as blade lateralfaces 12 and a portion of the region of the cutting blade portion 11located most distant from the rotational axis X and extending from thepair of blade lateral faces 12 toward their projecting sides will bedesignated as a blade tip face 13. Further, a blade bottom portionformed continuous from the pair of blade lateral faces 12 will bedesignated as a blade bottom face 14. Also, as a projecting side endportion of the cutter 10 in the direction along the rotational axis X isshaped substantially flat to be perpendicular to the rotational axis X,thus forming a cutting blade face 15. With this, by the edge at theboundary position between the pair of blade lateral faces 12 and thecutting blade face 15 and the edge at the boundary position betweenblade tip face 13 and the cutting blade face 15, a cutting operation ismade possible.

Of the pair of blade lateral faces 12 of the cutter 10, one on thedownstream side in the driven rotational direction S will be designatedas the leading side and the other on the upstream side in the drivenrotational direction S will be designated as the trailing side,respectively.

At the time of a cutting operation, the leading side blade lateral face12 comes into contact with the work 1 before the trailing side bladelateral face 12. When thicknesses of cutting chips generated at the timeof cutting operation, it can be confirmed that the cutting chipsgenerated on the trailing side have greater thickness than the cuttingchips generated eon the leading side.

Further, as shown in FIG. 5, it may be understood that the blade bottomface 14 of the cutter 10 is not involved in cutting and the portions ofthe pair of blade lateral faces 12 closer to the blade bottom than alimit line L are not involved in cutting, either.

[General Description of Manufacturing of Cutter]

FIG. 4 shows an outline of a manufacturing process of the cutter 10. Inthis manufacturing process, as shown in the same figure, a material suchas high-speed steel is turned on a turning lathe or the like to producea blank M having a cylindrical shape about the rotational axis X (#01).Next, in an outer circumference of this cylindrically-shaped blank M, agrinding machining by a hob machine or the like is effected to form theplurality of groove portions 10A helically about the rotational axis X.With this, at positions between each adjacent pair of groove portions10A, the plurality of cutting blade portions 11 are formed (#02). Thecutter 10 formed in this way is at its roughly cut state, in which ofeach cutting blade portion 11, at position facing the groove portion10A, the pair of blade lateral faces 12 are formed and at the portionextending to the projecting side of the cutting blade portion 11 (theportion distant from the rotational axis X), the blade tip face 13 isformed and at the end portion in the direction along the rotational axisX, the cutting blade face 15 is formed (see FIG. 5).

In this way, as the degree of involvement in the cutting can differbetween the leading side blade lateral face 12 and the trailing sideblade lateral face 12, the leading side blade lateral face 12 and thetrailing side blade lateral face 12 are formed in non-symmetry. For thisreason, in this manufacturing process, at the step #02, the leading sideblade lateral face 12 and the trailing side blade lateral face 12 arereformed into symmetry and by a grinding operation subsequent thereto,these are finished into non-symmetry. Incidentally, at the time ofgrinding at step #02, the grinding operation can be effectedalternatively to form the pair of blade lateral faces 12 into thenon-symmetry.

Thereafter, the roughly cut cutter 10 is subjected to a heat treatment(#03). After this heat treatment, one of the pair of blade lateral faces12 is ground by a first grindstone W1 (#04), and then the other of thepair of blade lateral faces 12 is ground by a second grindstone W2(#05). Thereafter, the blade tip face 13 is ground by a third grindstoneW3 (#06). Though not shown in this figure, during these steps or at theend thereof, grinding of the face of the cutting blade face 15 iseffected, whereby the pair of blade lateral faces 12, the blade tip face13 and the cutting blade face 15 are finished into predetermined shapeswith high precision, thus completing the cutter 10. Further, the step#04 corresponds to what is designated as “a first grinding step” in thepresent invention, the step #05 corresponds to what is designated as “asecond grinding step” in the present invention, and the step #06corresponds to what is designated as “a third grinding step” in thepresent invention, respectively.

In the present embodiment, the order of grinding is set such that thestep #04 (the first grinding step), the grinding operation of theleading side blade lateral face 12 of the cutting blade portion 11 iseffected and at the step #05 (the second grinding step), the grindingoperation of the trailing side blade lateral face 12 of the cuttingblade portion 11 is effected. Incidentally, this order can be reversed.Further, in the present invention, the order of grinding can be set alsosuch that the grinding operation at the step #04 (the first grindingstep) and the grinding operation at the step #05 (the second grindingstep) can be effected in alternation or that the grinding operation atthe step #04 (the first grinding step) and the grinding operation at thestep #05 (the second grinding step) are effected simultaneously.

In particular, when the grinding operations are effected at the step #04and the step #05, adjustment of blade thickness is realized by movingone of the first grindstone W1 and the second grindstone W2 or both thefirst grindstone W1 and the second grindstone W2 in the circumferentialdirection about the rotational axis X relative to the roughly cut cutter10, by an amount needed for this blade thickness adjustment. This modeof grinding is a technique identical to that of lateral dislocation inthe case of adjustment of tooth thickness of a gear and finishing to arequired blade thickness is possible without changing the blade shape(corresponding to the tooth shape of the gear).

Incidentally, the grindstones described above are molded into adisc-shape by e.g. sintering of grinding gains having high hardness forgrinding or binding them with a binder. As the grindstones, grindstoneshaving suitable grain size values of grains for the sake of finishingsmooth the cut machined faces by the hob lathe or the like.

[Grinding Device]

FIG. 3 schematically shows an inventive grinding device for the cutter10. This grinding device is provided for realizing an inventive methodof grinding the cutter 10 and, the device is configured to automaticallycarry out the operations of the steps #04 through #06 with setting thecutter 10 after the heat treatment thereto.

This grinding device includes a cutter supporting section A forsupporting the roughly cut cutter 10, a first grinding section B forgrinding one blade lateral face 12, a second grinding section C forgrinding the other blade lateral face 12, a third grinding section D forgrinding the blade tip face 13 of the cutting blade portion 11, agrinding operational section E, a dressing section F and a grindingcontrolling section G for controlling the above sections.

The cutter supporting section A supports the cutter 10 rotatably aboutthe rotational axis X and includes an electric motor type rotationaloperational mechanism 21 for rotating the cutter 10 about thisrotational axis X. The cutter supporting section A further includes alinear operational mechanism 23 for converting a drive force from anelectric motor type rotational drive device 22 into a linear operationalforce for moving the cutter 10 along the rotational axis X.

This cutter supporting section A functions to rotate the cutter 10 aboutthe rotational axis X at the time of grinding of the pair of bladelateral faces 12 or the blade tip face 13 and also to move the cutter 10along the rotational axis X and this section A is controlled by agrinding object controlling section 24.

The first grinding section B includes the disc-like first grindstone W1supported to be driven to rotate about a first drive axis P1 and anelectric type first grinding motor M1 for rotatably driving this firstgrindstone W1. The second grinding section C includes the disc-likesecond grindstone W2 supported to be driven to rotate about a seconddrive axis P2 and an electric type second grinding motor M2 forrotatably driving this second grindstone W2. The third grinding sectionD includes the disc-like third grindstone W3 supported to be driven torotate about a third drive axis P3 and an electric type third grindingmotor M3 for rotatably driving this second grindstone W3.

The first grinding motor M1 of the first grinding section B, the secondgrinding motor M2 of the second grinding section C and the thirdgrinding motor M3 of the third grinding section D are controlled by agrinding motor controlling section 26.

The first drive axis P1 of the first grindstone W1, the second driveaxis P2 of the second grindstone W2, and the third drive axis P3 of thethird grindstone W3 are set to postures parallel to each other. Withthis arrangement, the posture of the grindstone is set to a targetposture whichever one of the first grindstone W1, the second grindstoneW2 and the third grindstone W3 is selected by rotation of a supportingdisc 31 as will be described later herein.

The grinding operational section E includes the supporting disc 31 of aturret type supporting the first grinding section B, the second grindingsection C and the third grinding section D, a movable base 32 rotatablysupporting the disc 31, and a base operational mechanism 33 for settingmovement and angle of the movable base 32. A gear portion 31A is formedin the entire circumference of the outer circumference of the supportingdisc 31 and the section E includes a selecting motor 35 for rotatablydriving a pinion gear 34 meshed with this gear portion 31A. Further, theselecting motor 35 is controlled by a grindstone selection controllingsection 36.

The base operational mechanism 33 has a function of effecting atranslation movement of the movable base 32 so as to move the grindstone(generic designation of the first grindstone W1, the second grindstoneW2 and the third grindstone W3) closer to or away from the cuttersupporting section A and a further function of setting an angle at whichthe grindstone is to come into contact with the cutter 10. In theinstant embodiment, the base operational mechanism 33 has a similarconfiguration to that of a robot hand. This base operational mechanism33 includes a plurality of electric motors (not shown) for effecting thetranslation movement and the angle setting of the movable base 32 andthese electric motors are controlled by a grindstone setting section 37.

The dressing section F includes a diamond dresser 41 and a dresseroperational mechanism 42 for operating this diamond dresser 41. Thedresser operational mechanism 42 is provided for effecting an operationof a truing (reshaping) of a grinding face of the grindstone and has asimilar configuration to that of a robot hand. This dresser operationalmechanism 42 includes a plurality of electric motors (not shown) formoving the diamond dresser 41 along a predefined track and theseelectric motors are controlled by a dresser setting section 43.

The grinding controlling section G includes a microprocessor or a DSP,etc. and stores in its memory data for implementing automated grindingoperations and includes a program for executing a control operationbased on this data in the memory. This grinding controlling section Gcontrols the grinding object controlling section 24, the grinding motorcontrolling section 26, the grindstone selection controlling section 36,the grindstone setting section 37 and the dresser setting section 43.

[Description of Control]

With this grinding device, at the time of non-control, the grindstone ismaintained at its home position away from the cutter supporting sectionA and the diamond dresser 41 is maintained at its home position awayfrom the grindstone. Further, at the time of this non-control, thecutter 10 is maintained at its home position away from a grindingposition by the grindstone. Under this condition, as the control isinitiated with the roughly cut cutter 10 after the heat treatment beingsupported to the cutter supporting section A, the grindstone selectioncontrolling section 36 selects the first grindstone W1 as the grindstoneneeded for grinding and rotates the supporting disc 31 so as to movethis first grindstone W1 closer to the cutter supporting section A.

The first grindstone W1 includes, in its outer circumferential portion,a first grinding face Ws1 shown in FIG. 4 and FIG. 7 for finishing theleading side blade lateral face 12 into a predetermined shape. Thesecond grindstone W2 includes, in its outer circumferential portion, asecond grinding face Ws2 shown in FIG. 4 and FIG. 8 for finishing thetrailing side blade lateral face 12 into a predetermined shape. Thethird grindstone W3 includes, in its outer circumferential portion, athird grinding face Ws3 shown in FIG. 4 and FIG. 9 for finishing one ofthe blade tip faces 13 into a predetermined shape.

Next, the grindstone setting section 37 operates the movable base 32 toset an angle of the first drive axis P1 such that a virtual plane inwhich the outer circumferential face of the first grindstone W1 ispresent may assume a posture along a blade trace direction of thecutting blade portions 11 of the cutter 10 (posture corresponding to atwist angle of the cutting blade portions 11).

Though not shown in the figures, the cutter supporting section A isprovided with a sensor for detecting the positions of the pair of bladelateral faces 12 and the blade tip face 13 of the cutting blade portions11 of the cutter 10. Based on detection result of this sensor, thegrinding object controlling section 24 sets the rotational posture ofthe cutter 10 to an initial posture which corresponds to grinding of theleading side blade lateral face 12.

Under this setting condition, the grinding motor controlling section 26controls the first grinding motor M1 for initiating rotation of thefirst grindstone W1 and then the grindstone setting section 37 shiftsthe first grindstone W1 in the direction closer to the cutter 10.Further, simultaneously with this shifting, the grinding objectcontrolling section 24 moves the cutter 10 in the direction of therotational axis X and rotates the cutter 10 in synchronism therewithabout the rotational axis X.

With the above operation, the first grinding face Ws1 of the firstgrindstone W1 comes into contact with the leading side blade lateralface 12 of the cutter 10 as shown in FIG. 7 and under this contactingcondition, a grinding operation is effected on a region extending fromone end portion to the other end portion in the blade trace direction.At the time of this grinding operation, the first grindstone W1 ispresent at the fixed position and the cutter 10 is rotated about therotational axis X and also the cutter 10 is shifted in the direction ofthe rotational axis X, whereby the grinding operation in the regionalong the blade trace direction of the cutting blade portion 11 iseffected.

This grinding operation needs to be effected for all the leading sideblade lateral faces 12 of the plurality of cutting blade portions 11.Therefore, after completion of grinding of one blade lateral face 12, agrinding operation of another leading side blade lateral face 12 iseffected.

Incidentally, as a mode of controlling to be executed at the time ofgrinding a plurality of leading side blade lateral faces 12, it isconceivable to effect grinding of a blade lateral face 12 by the firstgrindstone W1 from the lower side to the upper side thereof (from thelower end side to the upper end side in FIG. 3) and then to effectgrinding of an adjacent leading side blade lateral face 12 from theupper side to the lower side thereof. Further, it is also conceivable toset a controlling mode such that after one leading side blade lateralface 12 is ground with moving the cutter 10 and the first grindstone W1in a predetermined direction relative to each other, an adjacent leadingside blade lateral face 12 is ground with relatively moving the firstgrindstone W1 in the same direction.

After completion of grinding of all the leading side blade lateral faces12, the grindstone setting section 37 sets the grindstone to its homeposition away from the cutter supporting section A. Under thiscondition, the grindstone selection controlling section 36 selects thesecond grindstone W2 as the grindstone needed for grinding and thegrinding object controlling section 24 sets the rotational posture ofthe cutter 10 to its initial posture corresponding to grinding of thetrailing side blade lateral face 12.

Under this set condition, after the grinding motor controlling section26 initiates rotation of the second grindstone W2 by controlling thesecond grinding motor M2, the grindstone setting section 37 shifts thesecond grindstone W2 in the direction closer to the cutter 10. Further,simultaneously with this shifting, the grinding object controllingsection 24 moves the cutter 10 in the direction of the rotational axis Xand rotates the cutter 10 about the rotational axis X in synchronismtherewith.

FIG. 8 shows roughly cut blade lateral faces 12 with two-dot chain linesand shows the blade lateral faces 12 ground by the first grindstone W1and the second grindstone W2 with solid lines, respectively. Similarly,FIG. 9 shows the blade tip faces 13 ground by the third grindstone W3with two-dot chain lines and shows the blade tip faces 13 ground by thethird grindstone W3 with solid lines, respectively. For facilitatingunderstanding, the amounts of grinding are shown with some exaggeration.

With the above operations, to the trailing side blade lateral face 12 ofthe cutter 10, the second grinding face Ws2 of the second grindstone W2comes into contact as shown in FIG. 8, and grinding is effected underthis contact condition on the region extending from one end portion tothe other end portion in the blade trace direction. By the grinding ofthe trailing side blade lateral face 12 by the second grindstone W2,grinding substantially same as the first grindstone W1 is effected.

Further, when the blade thickness is to be adjusted, this bladethickness adjustment is realized by moving the grindstone relative tothe roughly cut cutter 10 by an amount needed for the blade thicknessadjustment about the rotational axis X in the circumferential direction,in either one of the leading side grinding by the first grindstone W1and the trailing side grinding by the second grindstone W2.

After completion of grinding operations of all the trailing side bladelateral faces 12 as described above, similarly to the foregoing, withthe grindstone being set to its home position away from the cuttersupporting section A, the third grindstone W3 is selected as thegrindstone needed for grinding and the rotational posture of the cutter10 is set to the initial posture corresponding to grinding of the bladetip face 13.

With implementation of grinding by a process similar to the foregoingunder the above-described set condition, to the blade tip face 13 of thecutter 10, the third grinding face Ws3 of the third grindstone W3 comesinto contact as shown in FIG. 10 and FIG. 11, thus realizing grinding ofthe entire region in the blade trace direction.

Especially, when the grinding is effected by the third grindstone W3,this grinding will be effected in such a manner as to form the blade tipface 13 gaplessly continuous with the leading side blade lateral face 12formed by the grinding by the first grindstone W1 and the trailing sideblade lateral face 12 formed by the grinding by the second grindstoneW2.

When grinding operations are effected by the first grindstone W1, thesecond grindstone W2 and the third grindstone W3, wears will occur inthe respective grindstones. Then, the controlling mode is set such thata truing is implemented by causing the diamond dresser 41 of thedressing section F to come into contact with the grinding face beforethe shape of the grinding face of the grindstone changes significantlyfrom a desired shape due to such wear. And, the controlling mode is suchthat such truing is effected automatically when an accumulated period ofgrinding reaches a preset value.

When such truing is to be effected on the first grindstone W1, with thegrindstone being maintained at the home position, the first grindstoneW1 is rotated and to the first grinding face Ws1 under this rotatedstate, the diamond dresser 41 is caused to come into contact and thediamond dresser 41 is moved to copy a surface of the original firstgrinding face Ws1.

Such truing is effected similarly on the second grindstone W2 and thethird grindstone W3 also. Incidentally, this truing results in decreasein the diameter of the grindstone, which decrease will influence thegrinding because of an amount of displacement of the position of thegrinding face associated therewith. In order to eliminate suchinfluence, the grinding controlling section G provides a correctionvalue for each grindstone after its truing and sets the grinding face atthe appropriate position based on this correction value, for enablingappropriate grinding.

Function/Effect of Embodiment

As described above, according to the inventive grinding method and theinventive grinding device for realizing such grinding method, it ispossible to finish the shape of the leading side blade lateral face 12by grinding with the first grindstone W1 and to finish the shape of thetrailing side blade lateral face 12 by grinding with the secondgrindstone W2. In particular, since the leading side blade lateral face12 is ground by the first grindstone W1 and the trailing side bladelateral face 12 is ground by the second grindstone W2 with the roughlycut cutter 10 being supported to the cutter supporting section A, theseblade lateral faces 12 can be finished to required shapes even whenthese shapes 12 are non-symmetrical to each other.

Further, since the blade tip face 13 is formed gaplessly continuous withthe leading side blade lateral face 12 formed by grinding with the firstgrindstone W1 and the trailing side blade lateral face 12 formed bygrinding with the second grindstone W2, no stepped portion will beformed even at a boundary point V of the grinding region as shown inFIG. 11. With this, no stepped portion will be formed in the tooth faceof the gear formed in the work 1 and no stress concentration will occurat the boundary portion between the blade lateral face 12 and the bladetip face 13 at the time of cutting, so that the service life of thecutter 10 is extended also.

In case the blade thickness of the cutting blade portion 11 is to beadjusted, through displacement in the circumferential direction of thefirst grindstone W1 or the second grindstone W2, blade thicknessadjustment can be realized with a technique similar to that of lateraldislocation of a gear. Specifically, by increasing the grinding amountof the blade lateral face 12 with setting of the rotational angle of thecutter 10 about the rotational axis X, increase/decrease of the bladethickness of the cutting blade portion 11 is realized.

Incidentally, with the inventive grinding method of grinding askiving-work cutter and the inventive grinding device for a skiving-workcutter, a stepped portion can sometimes be formed in the blade bottomface 14 by grinding with the first grindstone W1 and grinding with thesecond grindstone W2. However, as this blade bottom face 14 is locatedmore on the center side of the rotational axis X than the boundary lineL, this is not a region affecting grinding of the work 1, so that thetooth surface formed in the work 1 will be smooth. Further, as no stressconcentration occurs in the blade bottom face 14 at the time of cutting,no deterioration occurs in the service life of the cutter 10, either.

OTHER EMBODIMENTS

The present invention may be configured as follows, in addition to theembodiment described above.

(a) As shown in FIG. 12 and FIG. 13, a “double-function” grindstone WThaving the first grinding face Ws1 of the first grindstone W1 as well asthe second grinding face Ws2 of the second grindstone W2 shown in theforegoing embodiment is employed for grinding the leading side bladelateral face 12 and the trailing side blade lateral face 12. Though notshown in the figure, this double-function grindstone WT is alsoconfigured as a disc type rotatable about an axis and the cutter 10 issupported to be rotatable about the rotational axis X similarly to theconfiguration shown in FIG. 3.

When grinding is effected by this double-function grindstone WT, asshown in FIG. 12, the first grinding face Ws1 is brought into contactwith the leading side blade lateral face 12 for its grinding andthereafter the cutter 10 is rotated by a predetermined angle to bringthe second grinding face Ws2 of the double-function grindstone WT intocontact with the trailing side blade lateral face 12 for its grinding.With repetition of these grinding operations, the leading side bladelateral faces 12 and the trailing side blade lateral faces 12 of theplurality of cutting blade portions 11 can be finished to desired faceshapes. Incidentally, FIG. 12 and FIG. 13 show the roughly cut bladelateral faces 12 with two-dot chain lines and the blade lateral faces 12ground by the first grindstone W1 and the second grindstone W2 withsolid lines, respectively.

Incidentally, in the case of effecting grinding with thisdouble-function grindstone WT, when the grinding of the trailing sideblade lateral face 12 is effected after grinding of the leading sideblade lateral face 12, adjustment of blade thickness is made alsopossible by setting of the amount of relative rotation between thedouble-function grindstone WT and the cutter 10.

Thereafter, as shown in FIG. 13, as grinding is effected with placingthe third grinding face Ws3 of the third grindstone W3 in contact withthe blade tip face 13, there is formed the blade tip face 13 gaplesslycontinuous with the leading side blade lateral face 12 formed by thegrinding with the first grindstone W1 and the trailing side bladelateral face 12 formed by the grinding with the second grindstone W2.

Especially, in this further embodiment (a) configuration, grinding ofthe region continuous from the blade lateral face 12 to the blade bottomface 14 is also possible. Thus, this region extending from the bladelateral face 12 to the blade bottom face 14 will be finished into asmooth arcuate shape, thus realizing improvement in the strength of thecutting blade portion 11. Further, in this configuration, in casegrinding of the other blade lateral face 12 is to be effected aftergrinding of the one blade lateral face 12, the outer end portion of thedouble-function grindstone WT is moved in the circumferential directionas being kept in contact with the blade bottom face 14, so that nostepped portion will be formed in the blade bottom face 14 and the bladebottom face 14 will be formed smooth.

(b) As the means for grinding the blade tip face 13 of the cutting bladeportion 11, it is also possible to employ a means rotated with placingthe blade tip face 13 into contact with a buff which is being driven torotate. In the case of grinding in the manner above, the buffimpregnated with polishing agent can be brought into contact with theblade tip face 13. In this mode of grinding, as the vicinity of theblade tip face 13 is also ground at the time of grinding of this bladetip face 13, it is readily possible to minimize a stepped portion in theboundary portion between this blade tip face 13 and the blade lateralface 12. With this, grinding for forming the blade tip face 13 gaplesslycontinuous with the blade lateral face 12 can be effected easily.

(c) As the means for grinding the blade tip face 13 of the cutting bladeportion 11, it is possible to employ a means effecting this by blastingshot peening material against the blade tip face 13, i.e. the so-calledshot blast or shot peening technique. In the case of grinding with suchmeans, as the shot peening material, it is possible to adjust thegrinding amount through use of hard grains or setting of the grain size.Further, in this mode of grinding, at the time of grinding of the bladetip face 13, the vicinity of this blade tip face 13 is also ground.Thus, it is readily possible to minimize a stepped portion in theboundary portion between this blade tip face 13 and the blade lateralface 12. With this, grinding for forming the blade tip face 13 gaplesslycontinuous with the blade lateral face 12 can be effected easily.

(d) The mode of grinding can be set such that the grindstone is movedalong the helically shaped groove portion 10A with the cutter 10 beingmaintained at a fixed position. With setting of the grinding mode inthis manner too, the pair of blade lateral faces 12 and the blade tipface 13 can be shaped into desired shapes.

(e) The grinding device can be configured such that its grindingoperational section E is arranged with the first grindstone W1, thesecond grindstone W2 and the third grindstone W3 being detachablymounted to an arm end of a single robot hand, so that the three kinds ofgrindstones may be selected one after another, as being enabled by thisdetachable mounting for effecting the grinding of the cutting bladeportion 11 of the cutter 10. In particular, in the case of employing theconfiguration wherein the grindstones are supported to an arm end of arobot hand, grinding can be effected in such a mode that the grindstoneare moved along the forming direction of the cutting blade portions 11(blade trace direction) without effecting rotation or movement of thecutter 10. Thus, the rotational operational mechanism 21 and the linearoperational mechanism 23 for the cutter supporting section A can beomitted.

(f) The grinding device can be configured with its grinding operationalsection E being arranged such that the movable base 32 is switchablewith its movement along a rail-like guiding mechanism between a positioncloser to the cutter supporting section A and a position distanttherefrom. Furthermore, it is possible to configure for allowing angleadjustment by tilting this movable base 32.

(g) The cutter 10 may be manufactured by forming helical groove portions10A in a blank M obtained by cutting material. Then, a cuttermanufacturing device can be configured by combining the inventivecutting device with a grinding device for effecting grinding of bladelateral faces 12 and blade tip faces of the cutter 10 thus manufactured.

INDUSTRIAL APPLICABILITY

The present invention can be used for manufacturing of a skiving cutter.

1. A method of grinding a skive-machining cutter having a plurality ofcutting blade portions formed by forming a plurality of groove portionshelically about a rotational axis in an outer circumference of amaterial so that the plurality of cutting blade portions are arranged atpositions between respective adjacent pairs of the groove portions andradially about the rotational axis, the method comprising: a firstgrinding step for grinding one of a pair of blade lateral faces facingthe groove portion; a second grinding step for grinding the other of thepair of blade lateral faces; and a third grinding step for grinding ablade tip face in a region extending from the pair of blade lateralfaces to a projecting side of the cutting blade portion; wherein anorder is set such that the third grinding step is effected after thefirst grinding step and the second grinding step; and wherein in thethird grinding step, a grinding operation is effected such that theblade tip face formed by grinding is formed steplessly continuous withthe one blade lateral face formed by the first grinding step and theother blade lateral face formed by the second grinding step.
 2. Themethod of grinding a skive-machining cutter according to claim 1,wherein the first grinding step employs a disc-like first grindstonehaving a grinding face having a shape along the one blade lateral faceand driven to rotate for the grinding operation and the second grindingstep employs a disc-like second grindstone having a grinding face havinga shape along the other blade lateral face and driven to rotate for thegrinding operation.
 3. The method of grinding a skive-machining cutteraccording to claim 2, wherein the third grinding step employs a thirdgrindstone having a grinding face along the blade tip face and driven torotate for the grinding operation; and the blade tip face formed by thisthird grindstone is formed continuous with the one blade lateral faceformed by the first grindstone and the other blade lateral face formedby the second grindstone.
 4. The method of grinding a skive-machiningcutter according to claim 2, wherein the grinding operation of the bladelateral face is effected by moving at least one of the first grindstoneand the second grindstone toward a circumferential direction about therotational axis by an amount needed for adjustment of blade thickness.5. The method of grinding a skive-machining cutter according to claim 1,wherein in the third grinding step, the grinding operation is effectedby buff or blast of shot peening material.
 6. A device for grinding askive-machining cutter comprising: a cutter supporting section for askive-machining cutter having a plurality of cutting blade portionsformed by forming a plurality of groove portions helically about arotational axis in an outer circumference of a material so that theplurality of cutting blade portions are arranged at positions betweenrespective adjacent pairs of the groove portions and radially about therotational axis; a first grinding section for grinding one of a pair ofblade lateral faces facing the groove portion; a second grinding sectionfor grinding the other of the pair of blade lateral faces; a thirdgrinding section for grinding a blade tip face in a region extendingfrom the pair of blade lateral faces to a projecting side of the cuttingblade portion; and a controlling section for controlling the device suchthat grinding operations by the first grinding section and the secondgrinding section are effected on the skive-machining cutter supported tothe cutter supporting section and then a grinding operation is effectedby the third grinding section for forming the blade tip face steplesslycontinuous with the one blade lateral face formed by the first grindingstep and the other blade lateral face formed by the second grindingstep.
 7. The method of grinding a skive-machining cutter according toclaim 3, wherein the grinding operation of the blade lateral face iseffected by moving at least one of the first grindstone and the secondgrindstone toward a circumferential direction about the rotational axisby an amount needed for adjustment of blade thickness.
 8. The method ofgrinding a skive-machining cutter according to claim 2, wherein in thethird grinding step, the grinding operation is effected by buff or blastof shot peening material.